Process of treating cadmium bearing materials



Nom 29, l938 w. H. LEVERETT PROCESS OF TREATING CADMIUM BEARINGMATERIALS Filed July 29, 1937 resulting gases as fumes I the gases.

UNITED STATES PATENT Aori-u :i-j.

sulphides.

PROCESS OF TREAT'ING CADMIUM BEARING MATERIALS Warren H. Leverett,

to National Zinc N. Y.,

Bartlesville, Okla., assignor Company, Inc., New York, a corporation ofNew York This invention relates to the process of treating cadmiumbearing materials, and particularly those cadmium bearing products of azinc ore sintering plant which contain cadmium and zinc In the recoveryof cadmium from cadmium bearing zinc ore it has been found diicult toobtain a sumcient percentage of the cadmium without the use of thedigesting pot, which is used for sulphating the insoluble cadmium. Thishot operation is not only disagreeable, but is also very expensive andin many instances is prohibitive.

The present invention contemplates the method of treating cadmium in atleast a part of bearing material, wherethe cadmium is in the form of asulphide, and it may also contain cadmium sulphate, cadmium oxide,cadmium sulphite, and other metals, to produce a relatively purecadmium. While any cadmium containing material may be treated by thismethod, it is primarily intended for bearing materials such tained froma zinc ore use with those cadmium as fumes and dust obsintering plant.

In the sintering operation, the cadmium and other associated metals arecarried away in the and fine dust particles.

These particles are collected by suitable known methods, such asltration in a dust collector Vor by electrical precipitation.

Reference will now be had to the accompanye ing drawing, wherein thevarious steps of the -method are shown diagrammatically with suitablelegends to make clear the invention.

. The gases carrying compounds of various metals from the vsinteringmachine pass through conduit A to the dust collector B. where the smallmetal bearing particles are separated from A quantity of this dust ofmetal bearing particles is mixed with a suicient quantity of water toform a resultant mix suitable for pumping. 'I'his mixis made in acontainer C, having a mixer D. nected with the lower by means of aconduit G from the pump enters into the mix trols the ow A pump E isinterconportion of container C F, and the delivery pipe container C andextends contained therein. Valve H conof mix from container C to thepump E. The liquid chlorine tank I is interconnected with conduit Fbetween valve H and the pump by means of pipe J. A throttle valve K inpipe J and adjacent tank I is adjustable to vary the release of liquidchlorine, which,

when released, expands object of the conduit to a gaseous form. Thepipes', pump valves and chlorine tank is to provide a mix with asufcient quantity of gaseous chlorine to react with all the oxidizablesubstances present in the' solution.

,The presence of the chlorine gas in the mix 5 will change all theinsoluble forms of cadmium into soluble forms, and will also eliminateall sulphur dioxide.' If the sulphur dioxide is not removed,objectionable cadmium sulphide will be formed when metallic zinc isadded to precipitate the cadmium.

During the chlorination process, a sufcient quantity of soda ash may beadded through pipe L to the mix to maintain the acidity thereof at a lowpoint.

Since all the forms of cadmium, the sulphide, are soluble through theincluding action of the insoluble solids by iiltration. By means of pumpM the chlorinated mix is removed from container C through pipe N to thefilter press O where all of the insoluble solids, including the leadsulphate, are filtered out. A suilcient amount of water must always bepresent in the solution to dissolve all the cadmium salts or compoundsformed.

The solution containing the cadmium is now removed from the lter pressto container P through co-nduit Q by pump R. Metallic (dust) zinc is nowadded'through chute S to the solution in sufcient quantities toprecipitate all the cadmium, thereby producing metallic cadmium in theformcf a sponge. The precipitation of cadmium with zinc dust tends toneutralizethe solution, therefore suiiicient sulphuric acid is addedthrough pipe T to maintain the solution slightly acid. By means ofgravity the zinc treated solution is ilowed through pipe V to thecentrifugal separator W where the cadmium is separated from the liquidand collect'ed as a sponge.

. This cadmium sponge may be further treated to produce a purer productby drying the sponge at about 125 C. in the absence of free oxygen.

.This may be accomplished in the atmosphere parent that the cadmiumbearing material will yield substantially all its cadmium due to thefact that a sufficient. amount of vwater and chlorine will completelydissolve all the cadmium, regardless of its original composition. Thesintering of zinc ore containing cadmium, usually as a sulphide, resultsin the formation of cadmium oxide, cadmium sulphate, cadmium sulphiteand cadmium sulphide. At ordinary temperatures the CdSO4 is dissolved bywater, CdO is dissolved by acid or chlorine, the sulphite is dissolvedby H2SO4HC1 and chlorine, while the cadmium sulphide is dissolved onlyby the chlorine. It is therefore apparent that the cadmium in all itsusual forms is soluble in a solution containing a` suicient quantity ofWater and chlorine. Cadmium so dissolved may be readily precipitated bythe addition of metallic zinc to produce a commercial cadmium sponge. Asstated above, this cadmium sponge may be puried by distillation or byany other known method.

While I4 have quite specifically set forth the different steps of thismethod and have definitely included cadmium bearing materials, such asore obtained from the fumes and dust produced by sintering zinc ore, yetit is desired to be limited only by the scope of the appended claims.

What I claim is:

l. The process of treating cadmium bearing materials comprisingintroducing chlorine into said cadmium bearing material, in the presenceof water, to cause the undissolved cadmium compounds to go intosolution; separating the insoluble matter from said solution; addingmetallic zinc to said solution to precipitate said cadmium; and removingthe liquid from said precipitate.

2. The process of treating cadmium bearing 'products from a zinc oresintering plant comprising intermixing chlorine with said cadmiumbearing products in the presence of water to dissolve the waterinsoluble cadmium and zinc compounds; removing the insoluble matter fromthe liquid; adding metallic zinc to said liquid to precipitate thecadmium; then removing the liquid from said precipitate.

3. The process of treating cadmium bearing fumes and dust from asintering plant comprising introducing chlorine gas into said fumes anddust, in the presence of water, to dissolve the then undissolved cadmiumcompounds; separating the insoluble material from said solution; andadding metallic zinc to said solution to cause a precipitation of thecadmium therein.

4. The process of treating cadmium bearing materials from an oresintering plant comprising admixing chlorine with said material, in thepresence of water in suicient quantity todissolve all the cadmiumcompounds present; re-

- moving the insoluble material from said solution; adding metallic zincto said solution to precipitate the cadmium; and removing the cadmiumprecipitate.

5. 'I'he process of treating cadmium bearing materials from an oresintering plant comprising admixing chlorine with said material, in thepresence of water in suflicient quantity to dissolve all the cadmiumcompounds present; removing the insoluble material from said solution;adding metallic zinc to said solution to precipitate the cadmium;removing the cadmium precipitate; subjecting said cadmium precipitate toa heat just sufliciently high to distill the cadmium; and recovering thevaporized cadmium in any convenient manner.

6. The process of treating cadmium bearing materials from an oresintering plant comprising admixing. chlorine with said material, in thepresence of water in sufcient quantity to dissolve all the cadmiumcompounds present; `removing the insoluble material from said solution;adding metallic zinc to said solution to precipitate the cadmium;removing the cadmium precipitate; subjecting said cadmium precipitate toa temperature of approximately 125 C. to drive off all the water;subjecting said dried cadmium precipitate to a temperature sufficient todistill the cadmium; and recovering the vaporized cadmium by any of theknown means. p

7. The process of treating cadmium bearing materials from an oresintering plant comprising admixing chlorine with said material, in thepresence of water in sufficient quantity to dissolve all the cadmiumcompounds present; removing the insoluble material from said solution;adding metallic zinc to said solution to precipitate the cadmium;removing the cadmium precipitate; subjecting said cadmium precipitate toa temperature of approximately 125 C. to drive off all the Water;subjecting said dried cadmium precipitate to a temperature sufficient todistill the cadmium; condensing said vaporized cadmium; and redistillingsaid condensed cadmium and again recovering the vaporized purifiedcadmium by a suitable means.

8. The process of treating cadmium bearing materials from an orechloridizing sintering plant comprising admixing chlorine with saidmaterial, in the presence of water in sulcient quantity to dissolve allthe cadmium compounds present; /removing the insoluble material fromsaid solution; adding metallic zinc to said solution to precipitate thecadmium; removing the cadmium precipitate; subjecting said cadmiumprecipitate to a heat just suiliciently high to distill the cadmium; andrecovering the vaporized cadmium in any convenient manner.

9. The process of treating cadmium bearing materials .comprisingintroducing chlorine into said cadmium bearing material, in the presenceof water, to cause the undissolved cadmium compounds to go intosolution; separating the insoluble matter from said solution; addingmetallic zinc to said solution to precipitate said cadmium.

WARREN H. LEVERETT.

